In order to understand the mechanisms involved in the lubrication of the normally loaded synovial joint, we will study the transport of fluid across the articular surface. The mechanism of transport, together with the time constant associated with the volumetric flows, will be determined. We are developing a technique whereby specific radioactive labels are incorporated into components of the synovial fluid and these labeled components can be identified within the cartilage layer. Identification will have the degree of specificity to enable the determination of the relative concentration at each depth of penetration of the fluid for time constants of the order of magnitude of seconds. While the development of such an "in vivo" model is vital to the understanding of joint lubrication and articular cartilage nutrition, no such model for the study of fluid transport has been reported. We intend to establish the validity of an animal model for performing such studies and, combined with an engineering analysis, improve our knowledge of the mechanism of fluid transport within the cartilage layer.